Tuesday, December 14, 2010

On the PteroGoss front, I just came across a new paper that doesn't seem to have received much press online yet. A new paper by A.W. Kellner has appeared online concerning the taxonomy of the small but well-known pterosaur family Pteranodontidae. The abstract can be found here.

This paper is interesting in that it attempts to reverse some of the trends of the past few decades concerning pterosaur diversity, in some cases (in others it's merely a re-calibration of the old genericometer). Kellner erects two new species and ressurects a genus, Geosternbergia.

I first encountered Pteranodon sternbergi in Dave Peters' awesome picture book A Gallery of Dinosaurs and other Ancient Reptiles (which also probably instilled my OCD towards drawing scale diagrams). It took my young mind a while to register that this huge, tall/broad crested pterosaur belonged to the same genus as the familiar, backward-pointing-crested Pteranodon lonciceps that flew beside it. I have to admit that I though P. sternbergi just looked... cooler. In this kind of side-by-side comparison, they really don't looks like they belong to the same genus. But as always, genera are subjective things, and nobody doubted that P. longiceps and P. sternbergi were each others closest relatives (they even overlapped in time and geologic range).

P. sternbergi was first described by Harksen in 1966 as a species of Pteranodon, based on a skull which differed from other species by its tall, vertical crest. In 1972, Miller placed it rather arbitrarily in its own subgenus, as Pteranodon (Sternbergia) sternbergi. The name Sternbergia turned out to be pre-occupied (as far as I know, subgenenus names compete with genera for priority). Miller amended the name to Geosternbergia in 1978.

However, this designation fell out of favor by the 1990s, when Chris Bennett published a couple of hefty reviews of Pteranodon from the Niobrara and related formations in Kansas. Bennett stramlined Pteranodon taxonomy, taking the several species that had been considered valid up to that time and showing that much of the variation was likely due to age and/or sexual dimorphism. For example, Bennett re-affirmed the idea that some small-crested Pteranodon specimens represent females (and some juveniles) of the same species as the longer-crested adult males. With this variation in mind, he suggested that all Pteranodon specimens could fit into two species: P. lonciceps and P. sternbergi. Because differences between species are limited almost entirely to the skull and crest (though Kellner 2010 suggests that some consistent differences may be found in the skeleton with further study), Bennett had to rely mainly on stratigraphic position to decide which species a specimen belonged to. While the two did overlap in time, it was only for a very brief period, so even though skulls are very rare compared to skeletons, a specimen from the lower Niobrara could be confidently referred P. sternbergi, while one from higher in the formation probably came from P. longiceps. (Image at left: illustration of various Pteranodon skulls by Matt Martyniuk, licensed).

One problem with this method, which Kellner points out in his new paper, is that many specimens (especially those recovered back during the days of Cope and Marsh) lack information about their provenence detailed enough to allow such an assignment. Bennett himself simply referred these to Pteranodon sp., but if Kellner's new work holds up, they'd need to be assigned even more broadly, only to indeterminate Pteranodontidae.
That's because Kellner has re-assessed the variation within the traditional grouping known as Pteranodon, and found some specimens that seem to represent new species among them. For me, the most interesting is Dawndraco kanzai, or "Kanza Dawn dragon" named for Dawn, apparently an Iroquois sky goddess, not the English word. The type and so far only specimen is UALVP 24238, a really interesting nearly complete skull and skeleton usually attributed to P. sternbergi (as in Bennett, 1994). Aside from being one of the most complete (former) Pteranodon specimens, it has always struck me as very, very odd. One of the primary reasons for making this a new species it its upper jaw. In most Pteranodon skulls (though none are as complete as you may assume based on its ubiquity in paleoart), the jaws can be seen to curve upward toward the tip and taper off into a needle-sharp projection at the tip. In the Dawndraco holotype, the preserved portion of the jaws are extremely long relative to the rest of the skull, but show no signs of tapering. In fact, the top and bottom margins of the upper jaw form essentially completely parallel lines up until the break. Letting your imagination fill in the rest, this must represent either a phenomenally long-billed animal, or one with a very unusual fat, somewhat flattened tip. The bone within this tall, long bill looks like a loose, honeycomb mesh of very thin struts. Taken together, this does seem like it probably comes from something fairly different than Pteranodon proper. (Image at right: Skull of Dawndraco, from Kellner 2010. Scale bar = 500mm).

The next new species is Geosternbergia maysei. Kellner considers Geosternbergia a distinct genus based on its unique skull characteristics, but again, there is currently no analysis to suggest that it is any more or less closely related to Pteranodon than anything else, so it remains a subjective decision (though it would be interesting to see someone perform an analysis using all of Kellner's species and Nyctosaurus). Anyway, G. maysei is named for a partial skull (KUVP 27821) from the South Dakota Sharon Springs formation. It was a large individual that Bennett previously referred to P. longiceps. However, Kellner notes that the crest is inclined further upward than it should be for that species, and that the premaxilla is arranged differently in forming part of the crest. It also appears to have a larger nasoantorbital fenestra, and a lower and larger temporal fenestra, than in G. sternbergi.

How well either of these identifications remains to be seen. I'm more inclined to be convinced by Dawndraco than G. maysei, simply because the very strange bill of the former seems harder to explain by age or gender variation. Kellner has also tended to be the 'leader' of one 'camp' when it comes to pterosaur taxonomy, usually opposed to Dave Unwin -- see their drastically different recent taxonomies of the ornithocheirids, for example. It will be interesting to see not only if these new species are accepted, but by whom.

While on the subject of new pterosaurs, two new species have also just been reported from the mid-Jurassic Tiojishan formation, some with soft tissue: Kunpengopterus sinensis and Darwinopterus linglongtaensis seem to add support for a monophyletic group of Tiaojishan pterosaurs somewhat intermediate between pterodactyloids and "rhamphorhynchoids", the Wukongopteridae. If I have time to read the paper more closely I'll try to follow up with a full post on these guys.

Sunday, December 12, 2010

[Above: Photo of the type specimen of Juravenator under UV light. From Chiappe & Göhlich, 2010.]

This month, Luis Chiappe and Ursula Göhlich published the first real English-language follow-up paper on the small German compsognathid Juravenator starki (named for its discovery at Stark Quarry near the Jura mountains, which also gave their name to the Jurassic period). You may remember this critter causing a stir when it was first described in 2006. Juravenator was the first non-avialan theropod found from the limestone deposits of Germany and France (which have also yielded Compsognathus and Archaeopteryx) to preserve clear, fairly extensive impressions of its skin and other soft tissue.

The specimen was discovered in 1998, but as far as I know news of this discovery first hit the Internet back in 2001, by way of a German-language news story reported to the DML. The new fossil was nicknamed "Borsti", from the German borstig, meaning "bristly." As some early-release photos show, at this point much of the fossil was not yet prepped, and the bulk of the skeleton was still encased in rock. I remember getting my hands on some photos from the early 2000s showing only the skull exposed, with no trace of soft tissue. Nevertheless, being a compsognathid, scientists fully expected that in life, this animal would have been covered in short, bristly stage 1 or 2 (in Richard Prum's model of feather evolution) protofeathers like its close relative Sinosauropteryx prima.

By 2006, the whole skeleton had been exposed, along with unexpected soft-tissue traces. While limestones from this area are world famous for their preservation of feathers, this is usually limited to the large, vaned feathers present on the wings and tails of aviremigian birds (those with feathered wings like Archaeopteryx). Small theropods like Compsognathus usually preserve very little, if any, soft tissue traces, and even the down-like or proto-feathery body covering of Archaeopteryx is only very rarely preserved, and then only as the faintest wisps in the rock. For this reason, even though the two known specimens of Compsognathus itself didn't preserve any feathers, it wasn't necessarily scaly all over (only a few hints of possible scales have been noted from the tail of one specimen, and even interpretation of those has been ambiguous).

So, when Göhlich and Chiappe described Juravenator, they may have been surprised to find extensive and well-preserved soft tissue surrounding the tail and part of the legs, showing very clear impressions of small, bumpy scales like those known of more primitive theropods and most sauropod and ornithischian dinosaurs. [See photo at right, from Chiappe & Göhlich 2010]. This caused a bit of a scandal, and rendered the name Borsti ironic: here was a specimen which phylogenetic bracketing methods predicted feathers, but the prediction failed. A number of explanations were offered for this. It could be that our phylogenetic analyses were off: that is, Juravenator was not a compsognathid at all, but something more primitive, having arisen before the origin of feathers. Alternately, since impressions were known only from the tail, it could have been feathered elsewhere on its body.

The first suggestion was complicated by the fact that the relationships of primitive coelurosaurs are notoriously poorly understood (some later analyses even found Juravenator to be more advanced than compsognathids), not to mention that the only known specimen came from a juvenile, so testing its relationships are a tricky proposition to begin with. The second suggestion, that Juravenator was only partly feathered, sounded a bit like special pleading given that there was only absence of evidence to go by.

The first hint that the second explanation may have been correct came in a little-known German-language follow-up paper published by the original authors later in 2006 in the journal Archaeopteryx. Apparently, this paper reported that, on closer examination, very faint, thin impressions of some kind of filament were present on the top edge of the tail. But that was all we had to go on until this month, when the complete osteology of the specimen was published.

Examination of the specimen under UV light (performed by H. Tischlinger, one of the co-authors of the paper in Archaeopteryx) has revealed more soft tissue than reported in the description. Additional impressions of scales can be seen under UV on the snout and lower legs, as well as the visible-light impressions on the tail. This new paper confirms the 2006 reports of proto-feather-like filaments on parts of the tail. As expected for these deposits, the feather remains are very poorly preserved, and only the tips are evident. But their size and arrangement seems to closely match those of Sinosauropteryx [see diagram at left, from Chiappe & Göhlich 2010]. Additionally, these impressions lie above the level of the clear, in-tact scale impressions. Impressions of internal tissues, including what may be collagen, can also be seen under UV below the scales and between the vertebrae. This makes the standard interpretation of the filaments as frayed collagen fibers by the birds-are-not-dinosaurs crowd pretty much impossible.

So what does all this mean? Clearly, the second explanation for the surprisingly "featherless" Juravenator seems to have been correct. As the authors note, it's possible that at this early stage of evolution, feathers and scales co-existed across the body of dinosaurs like Juravenator, and possibly even Sinosauropteryx and Dilong, where no scales are preserved but feathers are still found only in certain parts of the body. So far, this kind of co-existence of widespread scaly skin with fringes of feathers has only been known in the ornithischian Psittacosaurus but, they point out, it's not inconsistent with theoretical models of feather development and evolution. [Accompanying image: my life restoration of Juravenator starki from 2006. I'll have to update this to reflect the position of filaments on the tail.]

Of course, it is also possible that explanation #1 is also correct. The authors noted that compsognathids have sometimes been found to be an evolutionary grade, not a natural grouping. In studies which have found a natural, monophyletic Compsognathidae, only a few species (usually of Compsognathus, Sinosauropteryx and Huaxiagnathus) have been included in the analysis. More testing, with more included taxa, are needed to suss out where on the dinosaur family tree other supposed compsognathids belong.

Wednesday, October 20, 2010

Though Bob Bakker had been suggesting that small ornithpods dug burrows for years, on the basis of the kind of sediments the basal ornithopods of Montana were usually found in, we didn't get solid confirmation that these were really burrowing creatures until the discovery of Oryctodromeus. Here was an ornithopod with the same, vaguely burrower-like features as its relatives Orodromeus and Zephyrosaurus, but which was found inside an obvious burrow.

The burrow was the key, because aside from some fairly ambiguous skeletal details, these dinosaurs all had fairly standard ornithpod proportions: elongated necks, long (usually) stiffened tails (but see below), long hind limbs and short front limbs. The overall body plan was that of a bipedal runner, not a dinosaurian wombat.

While still far from mole or wombat like, the new dinosaur Koreanosaurus boseongensis (named by Min Huh, Lee Dae-Gil, Kim Jung-Kyun, Lim Jong-Deock and Pascal Godefroi) is even closer than its relatives. It has very robust forelimbs, and while the humerus is still long, the forearm is short and stout, with a massive scapula and coaracoid, and a big keeled breastbone, all of which indicate attachment sites for powerful muscles useful for digging. Interestingly, the hind limbs are also very specialized. They're relatively short compared to the forelimbs, with a low ratio between the femur and tibia lengths, and with short metatarsals. The length indicates that even if this wasn't a fossorial creature, it was probably a quadruped. The hip is especially interesting. The head of the femur, the bit which fits into the hip socket, is at a 135 degree angle to the rest of the bone. This would have given Koreanosaurus a very un-dinosaurian semi-splaying leg posture, similar to burrowing mammals. The authors speculate that it would have used its legs to brace itself inside an incipient burrow while it used its powerful forelimbs to shovel soil.

So, while the team of scientists was unable to locate any nearby fossil burrows big enough to have been made by this (roughly) meter long ornithopod, the skeletal details are more than enough to suggest a digging lifestyle. But it was no dinosaurian mole, as it still had many features in common with terrestrial dinosaurs, like a long neck and (presumably) long, partly stiffened tail. However, we shouldn't be so quick to assign stiffness to the tail just because this is found in other ornithopods. As I reported before, the Australian Leaellynasaura had an unusual, very long, very flexible tail.

Koreanosaurus was found in seaside cliffs of Boseong, on the south coast of Korea. It is the first Korean dinosaur known from good remains. It should be noted that another Korean dinosaur (a theropod) had previously been unofficially named "Koreanosaurus," but as this was a nomen nudum, it's no more a valid scientific name than "Sue," and is rightly ignored.

Sunday, October 10, 2010

Last time I reported on the odd case of a crazy new amateur paper on Morrison sauropod diversity, including the naming of a new species of Amphicloelias. I hoped that the SV-POWsketeers would comment on this situation, and they have. Be sure to check out this post and it's two follow-ups, as well as the comments (including comments by one of the paper's authors). The upshot is that "A. brontodiplodocus" has not been published, and the authors claim the current .pdf is an unfinished manuscript, but that they stand by their ridiculous conclusions nevertheless. As far as I know, because the name has only appeared in electronic form which is not recognized by the ICZN, "A. brontodiplodocus" can't even be considered a nomen nudum. It may be a nomen manuscriptum or something.

In more pleasant, mainly non-taxonomic quibbling news, SVP is happening right now! Those of us lucky enough to not be within a few hours drive of Pittsburgh for once in their lives (I kid!) but unlucky enough for that one time to coincide with the biggest paleo event of the year, can follow the interesting stuff in real time on Twitter, thanks largely to the efforts of Brian Switek of Lealaps, who is braving the conference's strict press policy and lack of free wifi to get the news out. Follow @Laelaps for hints about sampling biases, even more new, weird ceratopsians, how Euoplocephalus is over-lumped (early '80s favorite Scolosaurus coming back, I wonder?), and which bloggers are going to the bar tonight.

Wednesday, October 6, 2010

Dan Chure on the DML alerted us to this new, privately published monograph published without peer review (probably?) by an independent fossil digging/selling organization. It concerns a pretty damn remarkable looking bonebed from the lower Morrison Formation with several complete diplodocid specimens of various ages. This line from page 21 pretty much sums it up:

"The traditional approach would have provided us with two new species to add to the Morrison list of sauropods. Instead we employed a novel approach by attempting to fit previously reported Morrison fossils within the context of the A. brontodiplodocus sample. The results are astoundingly radical by comparison with previous studies."

I don't know what to say about this paper. It wouldn't surprise me THAT much if something like this were true but... really? Really guys? Fingers crossed that SV-POW or some some other sauropod experts take a look at this bad boy, though the stigma concerning privately held specimens may simply prompt everyone to ignore it. This is what Mike Taylor suggested on the DML, since he (correctly) pointed out that the hypothesis of the paper (all Morrison diplodocids are congeneric) is essentially unverifiable as long as the specimens are in a private collection and haven't been described in a peer-reviewed paper.

As it was independently published, questions about the newly named taxon's validity have been raised. But, really, is this any different from what Cope and Marsh were doing back in the 19th Century? If anything, cheap and easy publication has simply brought us back to those Wild West days of do-it-yourself science, spurious results and all.

Taxonomy aside, the baleobiological conclusions in this thing are... just... fascinating. and probably will NOT help the author's case.

Tuesday, October 5, 2010

Above: Restoration of Changchengornis by Matt Martyniuk, all rights reserved. Even when the colors of a prehistoric feathered dinosaur haven't been revealed by studies of feather microstructure, there are ways to infer which colors were and were not likely.

The recent discovery of a fossil penguin from Peru (click here or Ed Yong's take with heaps of pictures), complete with preserved feathers and melanosomes that reveal their color, prompted me to dive a little deeper into this topic. Keep in mind this is an area I'm still learning about myself, so please feel free to add corrections or keep the discussion going in the comments.

For those of us interested in palaeontography,* the recent work by Jakob Vinther (see original post here) and others on reconstructing the life coloration of prehistoric animals has been some of the most exciting paleontology research of the decade. In the carefree halcyon days before fossil melanosomes were recognized, I and other artists were given free reign over the external appearance of our feathered dinosaurs. But since Vinther's paper, I've been inspired to look into exactly what biological factors go into bird coloration. Needless to say, this is something not a lot of others have probably looked at, as most paleoart follows the old philosophy that when it comes to color, anything goes. Apparently though, this was far from true even before Vinther and his colleagues came along.

* Since this is John Conway's term I reckon I'm stuck using the Queen's preferred spelling, sorta like "pycnofibres". Anyway, that's just a fancy way of saying "paleoart".

There are several processes that add color to the feathers of birds and, presumably, other feathered dinosaurs. At the most basic level, these can be divided into structural color and pigmentation (though sometimes it isn't hat simple, as I'll explain down the page).

Structural ColorsStructural colors come from the actual physical structure of the feather. At the microscopic level, feathers exhibiting structural color have a "foamy" texture of tiny spheres or channels which enclose minute air bubbles. Light scatters through these bubbles in various ways depending on the exact arrangement. The development of these extremely complex structures has recently been covered by Dufresne and colleagues (2009), so you can track down that paper for a technical treatment of structural feather colors (there's also a good rundown of their research here).

Basically, structural colors can do two things: produce colors not found among the various pigments, and enhance or change pigment colors. For example, among amniotes, there is no such thing as a blue biological pigment. The blue feathers of a bird are produced by scattering due to structural colors. Similarly, iridescence as seen in many birds comes from the feather structure. A bird with bright white or pitch black feathers likely uses structural colors to achieve this effect--without them, these colors would be flatter, duller, and less vivid. Structural coloration can act as a filter, combining with pigments to form new colors. In most birds that have them, green feathers are produced by layering yellow pigmentation nodules over a "blue" underlying structure.

Does it fossilize?: You bet! Iridescent feathers have been reported by Vinther, and it's often apparently to the naked eye alone. There are some stunning examples of iridescent insect fossils out there. Structurally colored feathers have been recognized by a distinct arrangement where a thin layer of densely aligned melanin overlies a looser conglomerate of melanosomes. This can be seen even if the overlying keratin scattering layer has degraded away (Vinther et al. 2008). This kind of structure-via-melanin is also found in the dazzlingly iridescent plumage of hummingbirds (Prum, 2006).

What it means for dinobirds: Blue, green, jet black and bright white can't be present in dinobirds that lack structural color in their feathers. I've said before that structural colors are impossible in the monofilament integument of primitive coelurosaurs. However, I'm not so sure that's true. The main difference between hair and feathers isn't the structure of the filaments, it's the structure of the underlying molecules. Hair is alpha-keratin, a helix-shaped molecule like DNA. beta-keratin, which makes up feathers, has a layered and pleated underlying molecular structure more conducive to structural scattering. So a blue-fuzzed Struthiomimus may be possible. However, in the iridescent fossil feathers studied by Vinther et al. (2008), the structural color was restricted to the barbules, which are not present in many primitive feathered dinosaurs.

PigmentsMost bird colors are due in whole or in part to pigmentation, or lack thereof. There are several different kinds of pigments, with the two most common being melanins and carotenoids.

Melanins are what all the hubbub is about. Not only are these easily identified in fossil feathers, but their shape and concentration can tell you what color they gave their feathers. Melanins are responsible for black (though not deep, solid black, which require an extra push from structural color), gray, and a wide variety of browns through rufous orange colors. Melanins are the main pigment in mammalian hair, so think of the spectrum of mammal colors when imagining what shades are possible with melanin. A lack of melanin will produce white.

(Right: Different types of melanin in the feather of a Zebra Finch Taeniopygia guttata, from Not Exactly Rocket Science/Zhang et al. 2010).

Does it fossilize?: Of course! I've discussed the relevant melanosome papers in the past, posts linked below.

What it means for dinobirds: For carnivorous dinobirds, these are where the action is. Pure carnivores will usually lack the dietary requirements for carotenoids, so structural colors plus melanin are all they've got (and maybe porphyrins, see below). It seems odd that of the three described prehistoric dinobirds with color, they all seem to have the same color palate. Sinosauropteryx (rufous and white), Anchiornis (gray, black, white, brown, and rufous), and now Inkayacu (gray, white, and rufous-brown). These are all carnivorous/fish eating species, so it makes sense that they don't exhibit any more exciting colors. However, it's also possible that we're missing something: In their 2009 Anchiornis paper, Li and colleagues specifically noted that they didn't test for carotenoids. However, I would imagine that given their prior 2008 paper, they did look for structural color or at least iridescence in fossil feathers.

Carotenoids are, by and large, what give birds their characteristically bright colors. The trick is that carotenoids can't be directly synthesized by the body in animals (some can, but there need to be other types of carotenoids present to convert). Carotenoids come almost exclusive from a diet of plants or, secondarily, of things that sequester a lot of carotenoids in their body tissues (like plant-eating invertebrates and some fish). Gulls living near salmon farms have begun shown hints of pink in their feathers: this is because farm-raised salmon are fed artificial carotenoid sources to make their flesh pink, and these are transferred to the birds. The most unusual source of carotenoids, this time among a carnivorous species, is the Egyptian Vulture Neophron percnopterus, which gets its bright yellow facial skin by eating the droppings of ungulates, dropping which yield no significant nutritional value and appear to be eaten only for the carotenoids (McGraw, 2006)! Indeed, while carnivores aren't usually brightly colored, McGraw noted that there may be selective pressures in some species to add weird things to a diet in order to become more colorful.

Does it fossilize? Yes, but it looks the same as melanin, and unlike melanin, you can't tell a carotenoid by its shape. According to Li et al. (2009), special chemical tests would have to be run to determine if a melanosome is really a carotenoid, and what color it was.

What it means for dinobirds: Even though we haven't yet identified carotenoids in fossils, we know that they can only be present in animals that are herbivores or feed on herbivorous insects. Scansoriopterygids, for example, could have been brightly colored by carotenoids, since they presumably ate tree-dwelling arthropods. Alvarezsaurids would probably lack carotenoids if they are mainly termites and other social, non-colorful bugs, as has been suggested in the lit. Jeholornis and Jinfengopteryx, two dinobirds with direct evidence of seed eating, are prime candidates for reds, oranges, and yellows (or even greens, with added structural color). Also, keep in mind that red carotenoids from crustaceans, when eaten by birds with otherwise melanin-free feathers, are what give pink wading birds like flamingos their distinctive colors. This is why many artists restore some ctenochasmatid pterosaurs, especially Pterodaustro, as pink (though how all this applies to pycnofibres is still anyone's guess).

Carotenoids are often used by modern birds as a sign of fitness when choosing a mate. Because carotenoids have to be eaten, a bird with a poor diet will be drabber than a bird that is very successful at finding food. A flamingo kept in a zoo will turn white if its diet isn't artificially supplemented with red carotenoids.

Carotenoids can also impact the eye color of a bird, as well as beak color and the color of the scales on its feet... even the yellow yolk of a chicken egg is due to carotenoids (some birds use Flavin for yolk color, see below). Keep in mind that adding orange, yellow or green feathers, or red, orange or yellow beaks, implies your dinosaur is eating a diet containing carotenoids.

Porphyrins are perhaps most famous for lending blood its red color and leaves their green (both heme and chlorophyl are porphyrins), but it can also color feathers, adding browns and reds (and green, but only in the turacoverdin pigments found in Turacos). Interestingly, porphyrins may have a role in temperature regulation. In addition to insulating eggs (see below), they are mainly found in the downy feathers of nocturnal birds like owls, and those that are active in colder temperatures.

The blue of American Robin eggs is created by porphyrins, as is most other egg coloration. In fact, some researchers note a correlation between porphyrin in eggshells and nesting behavior. Pure white eggs are only found in birds which nest in shelter like under foliage, and which constantly attend their eggs. Species which leave the eggs partly exposed to the elements have colorful porphyrin-containing shells, possibly because of the supposed temperature regulating effect. Paleoartists might want to consider this when drawing various dinosaur nests.

Does it fossilize?: I'm guessing no, as we're dealing at the molecular level here. However, I wonder if porphyrins could be detected via chemical analysis, like the one used to detect beta keratin in the feathers of Shuvuuia deserti.

(Right: The juvenile Black-shouldered Kite Elanus axillarus uses porphyrins to achieve a red-brown color not found in adults. Photo by Mdk572, licensed.)

What it means for dinobirds: This one is the big question mark. I've never seen references that describe a method to detect porphyrins in fossils. Luckily, they're mainly only brown and dull red, colors that could conceivably be found with melanin alone. If anything, porphyrins give us license to add some extra reddish splashes to purely carnivorous dinobirds, especially those that may have been active at night or in cold climates, like troodontids.

Uncommon pigments: There are a variety of minor pigments that can color a bird's feathers. Pterins are responsible for the yellow, red, white, and orange colors of some bird eyes (in humans, eye color is controlled by melanin; low melanin results in blue eyes, and some babies eyes darken as the melanin levels increase). Flavin pigments cause many egg yolks to be yellow.

(Right: The feathers of a Yellow-headed Amazon Amazona oratrix. Parrots are so stingy with their carotenoids they had to evolve an entirely new pigment to color their feathers. Photo by Rei, licensed.)

Psittacofulvins are found only in (you guessed it) parrots, and create yellows oranges and reds in place of carotenoids, which parrots have evolved to sequester, possibly for nutritional reasons. There are some undescribed pigments known only in penguins that add florescence to their yellow display feathers.

The take-home message:When you add color to a feathered dinosaur restoration, you're presenting an implicit hypothesis about its diet, lifestyle, and soft tissue anatomy. when doing serious paleoart, keep these constraints in mind, and use them to make your art more interesting and your science more rigorous. Nobody can tell you not to draw a Utahraptor with a bright red face, but if you're trying to make paleontography and not just a bit of fun, why not depict it munching on a big, red fish or a pile of Sauroposeidon poop?

Thursday, September 16, 2010

Back in June, I reported on the sale of one of the famous crested Nyctosaurus specimens. A few weeks ago, Mark from a fossil selling site called DinoStar left this comment:

Not very accurate Matt. Frithiof is a very decent person who is doing a very legal business. Both KJ1 and KJ2 are still in the Brazos museum and are scheduled to be there for the next 2 years. KJ1 was sold to person who is constructing a museum. KJ2 is still for sale. Most private collections are eventually donated to a museum.

First, let me point out for the record I never said that what Frithiof and Mark do is illegal. As long as the fossils were obtained legally in the US, it's perfectly legal to sell them. That doesn't mean it isn't ethically questionable and actively detrimental to science, which I and pretty much 95% of the paleontological community would agree that it is.

Nevertheless, Mark shed some light on the nature of the infamous eBay sale. It's going to someone constructing a museum. What kind of museum or what kind of somebody remains a mystery. There are plenty of dodgy outfits out there calling themselves museums, and specimens in their collections may as well be in an 18th century cabinet of curiosity. A private "museum" is still a private collection unless the museum is somehow in the public trust, so it doesn't eliminate the hesitation most scientists would have of touching one of those specimens. But, as long as it's made freely available for study, this may be good news.

Or not, because even on Mark's own site, fossils currently on display in random small museums are being offered up for sale. For example, for only $19,000, I could become the proud owner of a Confuciusornis specimen with "scant restoration" and what looks to be an amazing anatomically incorrect ornithurine-like tail fan, straight "from China" which does not allow any exportation of fossils under any circumstances (though it does say it's from an "old collection", have the laws changed in 14 years since these birds first started turning up?). If I can buy my very own illegal Chinese pygostylian straight out of a museum's glass case, what's to keep the new owner of KJ1 from trying to cut his losses if the museum doesn't turn a profit?

KJ2, for what it's worth, is still for sale. So if you want to own a nearly one of a kind scientific treasure to hang up in your den, act soon. Maybe the Field Museum can take it off your hands in 50 years once you kick it?

Aside from cultural inertia, the answer Taylor gave is this: "As of 1st January 2000, a new ICZN ruling has come into effect, saying that a name that's been considered valid for fifty years can't now be replaced by one that's been considered invalid during that time." This is also the answer Mickey Mortimer gave in some (but not all) relevant entries on the current Theropod Database. Brian Switek, in an old Laelaps post, gave the same answer: Manospondylus hasn't been considered valid in 50 years, so it's a nomen oblitum ("forgotten name"). He also suggested that this means T. rex has "protected status" which would have to be overturned by the ICZN in order for M. gigas to become valid.

The problem is that none of that has any bearing on what "nomen oblitum" actually means according to the current ICZN code. The ICZN states that in order for a name to be declared a nomen oblitum, all of the following things need to be true:1. the senior synonym or homonym has not been used as a valid name after 18992. the junior synonym or homonym has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years3. a paper must be published citing evidence for #2, and citing both names together, declare that the junior synonym or homonym is being made a nomen protectum ("protected name") in accordance with ICZN article 23.9.

The confusion seems to come from #2. It's not a matter of the senior name not having been used in the past 50 years, but the junior name must have been used frequently enough in recent history in order to be eligible for conservation. Clearly, T. rex meets the second criteria. But what about the first and third?

For number one, the answer is I'm not sure, but I think so. It depends on what your definition if "is" is. Has Manospondylus been used since 1899? Definitely, yes, and in several papers, as Mickey Mortimer pointed out in the comments on my previous post on this topic. But was it used as valid? Most authors, even in the early 20th century, recognized that two vertebrae were pretty poor material to be basing a species on. Many of them considered it to be what we'd now call a nomen dubium ("dubious name"). For example, here's what Matthew & Brown (1922) had to say on the subject: "Osborn has already (1917) called attention to another fragmentary type, Manospondylus gigas, as possibly identical with Tyrannosaurus but based upon an inadequate type." They don't explicitly say it's valid or invalid (I'd like to know what Osborn 1917 actually aid on the matter but don't have that paper. Anyone?).

As for number three, it appears that the situation has never been adequately addressed in the literature, so the criterion is not satisfied. The issue came up in 2000, when Peter Larson claimed to have rediscovered the original Manospondylus locality, and more of the type specimen, confirming it is the same as T. rex. As far as I know, this has never seen print beyond an AP article (Anonymous, 2000. "Discovery could Endanger T.Rex Name." The Associated Press.)

In short, could M. gigas be a nomen oblitum? Maybe, depending on the meaning of "valid" and if somebody gets up the nerve to actually publish the case. Is Manospondylus a nomen oblitum as of right now? Definitely not, and it remains the valid senior synonym of Tyrannosaurus until and unless someone acts as revisor to the contrary.

Addendum: Just for fun, I looked up "valid" in the ICZN's glossary. Who better to determine what the ICZN means by valid than the ICZN? Here's the entry:valid, a. (validity, n.) Of an available name or a nomenclatural act: one that is acceptable under the provisions of the Code and, in the case of a name, which is the correct name of a taxon in an author's taxonomic judgment.

Since the Code does not formally recognize nomina dubia as invalid names (or at all, really), this seems to indicate that M. gigas was considered valid by all those authors in the 20th century, at least under the ICZN's definition. Matthew and Brown, for example, did not consider M. gigas an invalid name (a junior homonym, improperly coined, etc.), just non-diagnostic. Which as far as the rules are concerned, is A-OK. Sorry kids, barring an act of ICZN, M. gigas looks like it's on solid footing as a currently valid name.

Friday, September 3, 2010

Here's a really interesting idea floated by Andrea Cau (with help from Mickey Mortimer, Ville Sinkkonen, Rutger Jansma and Zach Miller) over at his Theropoda blog.

Everyone is making a big deal about Balaur bondoc, the apparently double-sickle clawed dromaeosaur. The double sickle idea comes from the very strange nature of the foot (close-up image in the last post, linked above).

The first sickle claw is present on the first toe. Normally, in non-avian theropods, the first toe is small and placed high on the foot, like the dew claw of a dog. Basically, it's vestigial. However, in lineages where the first toe evolves some kind of use, the entire metatarsal supporting the toe tends to descend, placing the first toe at the same level as the others. This is seen in two lineages of theropod: birds, where the first toe is used for perching, and therizinosaurs, where it's been re-adapted for walking. Animals that use four toes in walking (rather than having four toes but only using three) are called functionally tetradactyl.

So, did Balaur not use its enlarged first and second toes to kill prey as in other dromaeosaurs, but simply as extra walking digits, as in therizinosaurs? Balaur is certainly built like a therizinosaur, with short, stocky hind limbs and very weird hips. The hip bones of Balaur, as you can see in the image above, are extremely swept back. Some of this may be due to crushing, but probably not all. Normally, such a hip arrangement is seen only in herbivorous dinosaurs, which need to clear out space in the torso for their expansive, plant-fermenting guts.

Tim Williams on the DML has also pointed out that the atrophied hands with reduced third finger and fused wrist elements are also indicators of decreased predatory ability. The only other dinosaurs I can think of off hand that have such reduced third fingers are avialans and the herbivorous Caudipteryx (and, of course, alvarezsaurids and tyrannosaurids, but for different reasons). Avialans and Caudipteryx are the only ones that retain fairly normal hand proportions while shrinking the third finger.

Much has been made of the fact Balaur lived on isolated Romanian islands, and that the "island rule" probably had a lot to do with its weird anatomy. Could similar effects have led to this line of dromaeosaurs becoming fully herbivorous? Weirder things have happened to island dinosaur lineages. Just look at the kiwi.

The parallels between Balaur and therizinosaurs are hard to ignore, but obviously it would be helpful to have some skull material before definitely drawing any conclusions about its diet. In the mean time, check out the cool reconstruction Andrea included in his post for what a therizinosaur-mimicking dodo-raptor may have looked like.

Note that the two sickle claws are on digits one and two, and digit one is essentially anti-retroverted, pointing forwards as in therizinosaurs. Balaur also has a lot of fusion in the hand, with digit two and three fused together and digit 3 reduced, as in caudipterids. Balaur lived on the island of Hateg in Maastrichtian (latest Cretaceous) Transylvania, a location known for its insular dwarfism among herbivorous dinosaurs, including the dwarf sauropod Magyarosaurus and dwarf hadrosaur Telmatosaurus. While Balaur is about the size of the larger contemporary dromaeosaurs at around 2 meters in length, its unique suite of derived skeletal characters also fits into the "island rule," according to Sues in an accompanying write-up to the official paper. While herbivorous forms tend to "shrink" on islands to conserve resources, predators often grow larger to better exploit the dwarf herbivores, relatives of which would be out of their league elsewhere. A good example of this are the famously small, extinct Stegodon dwarf elephants of Flores (or indeed the apparently dwarf humans, Homo floresiensis), and the contemporary giant monitor lizards like the Komodo dragon. However, no teeth of any carnivore larger than Balaur have been found in the Hateg basin deposits. Teeth are usually the most numerous and obvious indicators of the local carnivore population, so Balaur was probably the largest predator in its ecosystem. This would seem to fit with its stocky build and double sickle claw: here was an animal that truly met the popular image of dromaeosaurs grappling with prey larger than themselves. The extra claws and solid build of Balaur would have come in handy when taking down a hadrosaur or sauropod.

Update: It seems like there's some confusion about the name. Tom Holtz on the DML, and some parts of the above NatGeo article, reported it as Baldaur bondac. Others (and other parts of the linked article) use Balaur bondoc. The later is he correct spelling.

Thursday, August 26, 2010

Just a quick note that the blog over at Bachelorsdegree.org is featuring DinoGoss among a multitude of far more worthy paleo-blogs, intended to be a list of resources for Paleontology students. I can't say I disagree with any of the selections, and most of these are mandatory subscriptions for anyone interested in paleo.

As you can probably tell, the main impetus for this post was as an excuse to use a picture from Back to the Future II.

While I'm here, and advertising myself, I might as well post a link to my ongoing attempt to put together a "field guide" to the lower Yixian Formation flora and fauna. You can check out the gallery at DeviantArt. And don't be afraid to comment on them, the harsher the anatomical nitpicks, the better!

Tuesday, August 3, 2010

By now many of you may have seen the headline on science news sites proclaiming that Triceratops has gone the way of Brontosaurus thanks to Scanella and Horner's new paper which suggests it may have been a sub-adult form of Torosaurus. If you understand the very rudimentary basics of science, you may be thinking, "WTF?"

Unfortunately, it should be clear by now that the vast majority of "science reporters" out there are among the most incompetent people being paid to ostensibly "do" the "job" of "reporting news" "accurately." I've already covered the backstory here. Needless to say, just because Triceratops is a juvenile Torosaurs doesn't mean it no longer exists, and furthermore Torosaurus is the newer name, so the name Triceratops is safe and sound (well, except from the shadowy threat of Agathaumas, but that's a different story). Also, David Orr at the awesome blog Love in the Time of Chasmosaurs has already addressed this failure of journalism and journalistic integrity. So I'll just add a few thoughts because really, this is just getting ridiculous.

You've heard it said before that most mainstream science reporters do not understand any single part of the subjects they're covering, and they can therefore be classed not only as useless, but as actively detrimental to human progress. Let's just accept that and call out a few of these hacks by name, shall we? Here are two articles that came up among the top hits when I typed "''Triceratops''" into Google, and are therefore doing the most damage to intelligence in the English speaking world.

Casey Chan, an apparently illiterate Gizmodo blogger, writes: "Scientists sure enjoy crushing my childhood memory of The Land Before Time (they nixed Brontosaurus a while back). Hopefully they won't delete Triceratops too." Immediately after this is a link to a site explaining why they won't, which Casey either read but did not understand or didn't bother to read at all.

Dan Satherley, 3 News NZ reporter of alarmist half-truths, writes: "It seems however that despite its juvenile status, its popularity with the public means that it'll be Torosaurus that ceases to exist. Horner says Torosaurus specimens will now be considered Triceratops." Yeah. You read right. This directly contradicts the headline. Unlike Casey, above, who is merely a simpleton, Dan read the original report, understood most of it (it's not the fact that Triceratops is popular that it remains valid, it's that it's the older name), and wrote the opposite as a headline in an effort to attract more hits. Classy. This is like beginning a review of the movie Backdraft with the headline "Fire in local theater kills dozens."

I should also mention that DinoGoss is not responsible for any head-desk collision injuries caused by reading the comments in these articles. You've been warned.

Thursday, July 22, 2010

Just a quick note on something I stumbled upon while checking out the new google image search. These paintings by Zhang Zong Da (click here!) are seriously cool, some of the most effective art I've seen portraying the Jehol and Dauhugou biota. My favorite is the third image down depicting pollinating insects. Reminds me of Microcosmos or something, an aesthetic I've tried for with some of my own digipaintings but not nearly at the same level of skill or effectiveness.

One idea I particularly like (and wonder why I haven't seen more often) is the Microraptor with "tailfins" like a '57 Chevy. As we all know, microraptorians had long pennaceous feathers not only on the metatarsus but the tibia (and the thigh in some cases, known as "butt fans"). All gliding micro restorations I've seen have the tibiae fully extended, creating a wide gap between the sticky-out biplane feathers of the metatarsals and the front wings of the arms. The restoration above shows the legs in a 'kneeling' posture, so that the tibia feathers stick more or less straight up behind the front wings, presumably creating a stabilizing effect. I don't know how aerodynamically sound this configuration would be, but it sure is a cool idea!

Monday, July 19, 2010

There's a lot going wrong with the Caudipteryx model pictured above, once prominently featured on the cover of a 1997 National Geographic. But maybe not as many things as you'd think.

Ever since I started drawing prehistoric animals for serious, I've been on a crusade to see that it's done right. Too many people draw feathered dinosaurs with zero background knowledge of how wings and feathers are put together or appear in life. One of my biggest pet peeves has been drawings of Caudipteryx which give it secondary feathers. That is, remiges that stem from the ulna. You see, Caudipteryx was one weird dinobird. It had fairly puny wings compared to its body size, with primary feathers only a little longer than the length of the hand. And, apparently, no secondaries. This gives the effect of small, narrow wings good only for flicking out in possibly short displays of small color flashes. All this is based on the holotype specimen of the type species, C. zoui. See my recent reconstruction above right.

However, I recently (finally) got my hands on the descriptions of the referred C. zoui specimen, C. sp., and C. dongi. The referred specimen of C. zoui (BMP 0001) shows the exact same arrangement of feathers as the type. C. dongi, on the other hand, aside from some subtle differences in postcranial proportions that may or may not allow it to be placed in a separate species, has something else: secondary feathers. Check it out:

Above: Portion of plate 1 from Zhou & Wang, 2000.

The photo is pretty poor quality, but you can clearly make out feathers coming from an area inboard of the wrist. The accompanying line drawing makes it more clear:

Above: Portion of figure 1 from Zhou & Wang, 2000.

Notice that in the photo, you can make out possible remains of a tightly banded color pattern also evident in the tail of the C. zoui holotype, but only on the secondaries.

So could C. dongi merely be a growth stage of C. zoui with extra wing feathers? Thanks to two specimens of Similicaudipteryx yixianensis (which are nearly identical to C. sp. in size, proportions, skull shape and even feathering), we know that at least some caudipterids possessed only primaries when they were juveniles and grew secondaries as they matured (the C. sp. specimen also has secondaries in the same proportional size). However, C. zoui is larger than the C. dongi specimen (and the secondary-possessing Similicaudipteryx/C. sp. specimens), so even if it is immature, it must be an immature specimen of an even larger species.

Keep in mind this is all based on published figures and rather poor photographs, so at the risk of sounding like Dave Peters, it would be great for someone with access to the physical specimens to confirm or deny this stuff. Sadly, very little about the actual feathers of the various specimens has been described in the lit, except for the holotype specimen, and even there, seemingly important things like the color bands are only mentioned in a figure caption. At any rate, feather coloration, length, and extent should be kept in mind when trying to determine which of these things, if any, represent distinct species.

Thursday, July 15, 2010

Today I read possibly one of the dumbest science news articles of all time, or at least the most condescending. Somewhere in here is news of an interesting study. English scientists have isolated the protein responsible for the formation of hard-shelled eggs in chickens, a step forward in developmental science that could potentially yield applications for materials science. So, how to make sure this mildly interesting study grabs the attention of Joe Six-pack? Put out a press release to every major media outlet claiming to have solved the "age old problem" (really?) of which came first, the chicken or the egg?

Not only is this silly eyeball-grabbing headline a blatant attempt to pander to the lowest common denominator and point out what a complete joke science reporting has become, it assumes the absolute worst about the reader's level of science comprehension and interest. And it's obviously completely wrong!

The articles in question "argue" that because a protein for forming eggshells is found inside chickens, this proves that the chicken came before the egg.

Not only is this severely flawed logic, you don't need a discovery to prove the answer one way or the other: If you really want an answer to this rhetorical philosophical conundrum, it's obvious using simple logic and knowledge of how evolution works.

Let's define some terms first. I think implicit in this old riddle is the fact that we're talking about chickens Gallus gallus and chicken eggs here, specifically.

Nothing in the report suggests that proteins for hard shells originated with modern chickens. In fact, we know from observation that all other bird species, including those more primitive than chickens, lay hard-shelled eggs (though as PZ Myers points out in the link below, they often use a different protein). We know based on fossil evidence that hard-shelled eggs were laid by not only non-avian theropods but also sauropods and ornithischians. In contrast, softer shelled eggs are found in crocodilians and pterosaurs. So we know that the hard-shelled egg this protein (or the genes coding for it or similar proteins) allows evolved among ornithodirans sometime after pterosaurs diverged but before ornithischian and saurischian dinosaurs split. So, let's ballpark it to the early-mid Triassic period for the appearance of hard-shelled eggs. Even allowing for the broadest possible definition of "chicken" (Galliformes), the earliest you can say chicken-like creatures walked he earth is the late Cretaceous, when the stem-anseriform Vegavis lived (so we know that the chicken line must have split from the duck line by that time).

That covers the hard shelled egg in general, which clearly came long before the chicken. What about modern chickens specifically and their eggs? This gets down to the biological species concept, of which there are many and they all overlap. Is a chicken anything that can successfully breed with any random clucker down at the farm? If so, we're getting into some sticky concepts of ring species and sub-species here, which just muddy the waters, especially when ancestral species are taken into account. Let's just say for our purposes, a "chicken" means the type specimen of Gallus gallus domesticus, and its specific genome. The species this bird belongs to, however you define it, diverged from an ancestral population that we can say was non-chicken. The relevant mutations or changes in allele frequency that define the line between chicken and non-chicken almost certainly did not occur inside the living adult non-chicken and were then passed on to its offspring in some kind of Lamarckian evolutionary event. Rather, they would have taken place in the cell divisions leading to the formation of the first true chicken egg.

Put more simply, a non-chicken did not spontaneously transform into a chicken via some kind of Fantastic Four style cosmic wave, and it did not spring spontaneously with all its essential chickenness in place from the head of Zeus. Rather, a non-chicken had to have laid an egg containing a chicken embryo. Can this be said to be a chicken egg, if it was laid by a non-chicken? I'd day yes, as it contains a chicken. Though ultimately, maybe this classic paradox is better left to philosophers after all.

PZ Myers of Pharyngula has done his own write-up on this travesty of science reporting and goes into more detail on the protein angle, well worth a read here. PZ says that "you simply can't make the conclusion the reporter was making here" but, given the prevalence of this exact conclusion in other articles from other news sources, everybody is simply copying one idiot science writer or, more likely, this conclusion was actively promoted by a press release. I can't decide which would be worse.

EDIT: This is getting hilarious. No, not the plethora of tragically inevitable comments from creationists, but watching the American media slowly realize that every single one of their science writers who allowed this nonsense to be repeated on their pages are being laughed at by people who took middle school biology, even in their own comments. Case in point: A single editor's note has been made on the CNN Article headline: "Maybe." Not, "Sorry, our so-called journalists are too stupid to recognize an obvious load of crap when they see it, or at the very least point out the crap being served to them in press release form. The people responsible have been fired and we're hiring a literate this time."

Available now!

Available in paperback & Kindle:

About Me

Matthew P. Martyniuk is an
illustrator and science educator
specializing in Mesozoic birds
and avian evolution. He has been
drawing prehistoric flora and
fauna since he first held a pencil,
and became fascinated with the
dinosaur/bird transition after
discovering a copy of Gregory S. Paul’s Predatory Dinosaurs of
the World at his local library. His
illustrations and diagrams have
appeared in a variety of books,
news articles, and television
programs from Discovery, the
Smithsonian, and the BBC, and
he publishes the paleontological
blog DinoGoss.